1. Field of the Invention
The invention relates to a flame glow unit for heating the combustion air for a combustion device, especially an internal combustion engine, of the type having a flame glow plug, which is placed in the air duct of the combustion device, a current supply device for the flame glow plug, a fuel supply device for the flame glow plug and a control device for the current and fuel supply of the flame glow plug.
2. Background of the Invention
A flame glow unit of the type mentioned above known, for example, from German published application nos. DE 33 42 865 C2 and DE 40 32 758 A1. Such a glow unit is used, for example, as a cold starting aid for the combustion device and especially for preheating the intake air and boost air of internal combustion engines, such as diesel engines, as well as for suppressing smoke in the waste gas during and after the starting phase.
In the flame glow unit known from German published application DE 33 42 865 C2, a switching device is provided as a control device, with which the heating element of the flame glow plug is quickly heated and is then further operated with reduced heating power, which is achieved by a fixed-cycle operation with a preset pulse to no-current ratio. This control is produced, in this case, by a temperature switch or a time switch.
In the flame glow unit known from German published application DE 40 32 758 A1, the control device is further designed so that the flame glow plug is provided both with current and with fuel in a synchronized manner.
In such flame glow units, it is desired that the processing of the fuel-air mixture for the flame glow plug takes place, optimally, over the entire load range of the combustion device, especially the entire load range and rpm range of the internal combustion engine. But, this optimal processing of the mixture does not exist in the case of the known flame glow units, since the operating conditions of the related combustion device are not sufficiently taken into consideration.